(1) Field of the Invention
The present invention relates to a monoaxially oriented polypropylene material which is excellent in the properties of moldability in the film fabrication process, fibrillation property after the orientation of the film, and also heat resistance, tear resistance, adhesive strength and so forth.
More particularly, the present invention relates to a woven or non-woven fabric made of the above material and a heat-resistant reinforced laminate material comprising the monoaxially oriented polypropylene material or the woven or non-woven fabric and a base material which are bonded together and which laminate material has excellent heat resistance and tear resistance. Furthermore, the present invention relates to a method for producing the above-mentioned woven or non-woven fabric and laminate material.
(2) Description of the Prior Art
There has been proposed a non-woven fabric which is prepared by laminating reticular webs formed by fibrillating longitudinally and monoaxially oriented multi-layer webs, and a woven fabric or a non-woven fabric which is prepared by crosswise laminating or weaving longitudinally and monoaxially oriented multi-layer tapes (hereinafter referred to as "woven or non-woven fabric"). They are practically produced using high-density polyethylene as disclosed, for example, in British Patent 47112/72 and U.S. Pat. No. 3,985,600.
More particularly, the woven or non-woven fabric made of high-density polyethylene is made by laminating low-density polyethylene layers on both surfaces of a high-density polyethylene film, then orienting the laminated films and fibrillating the film to obtain reticular webs. The fibrillated webs are laminated crosswise in which the axes of orientation intersect with each other, and then they are thermally bonded. These woven and non-woven fabrics have been utilized as agricultural and gardening materials as well as building materials such as covering materials for agriculture, green covers for a golf course, filters, bags for draining or other various uses, oil adsorbents, flower wraps and house wraps.
In recent years, however, with the tendency of increasing uses, the reduction in cost and the improvement in heat resistance, tear resistance, adhesive strength and so forth are demanded. In order to meet these demands, it is desired to develop a polypropylene non-woven fabric which has higher heat resistance than that of polyethylene non-woven fabric. As a heat-sealing layer (adhesive layer) for the polypropylene non-woven fabric, a propylene-ethylene random copolymer has usually been used. However, when the propylene-ethylene random copolymer is used as the adhesive layer, several troubles occur in various steps of production process such as a film fabricating step and a fibrillating step and the troubles inhibit the long and stable operation. In addition, there is a disadvantage that the final product of non-woven fabric having high adhesive strength and heat resistance cannot be obtained. Furthermore, in a reinforced laminate comprising a base material and a woven or non-woven fabric, when a polyethylene fabric is used, the formed laminate is poor in heat resistance.
Moreover, in the case of a polypropylene non-woven fabric using propylene-ethylene random copolymer as an adhesive layer, the film fabricating property, fibrillation property, adhesive strength between webs forming the non-woven fabric and heat resistance are not sufficient.
Nowadays, with the increase of the use of woven and non-woven fabrics for draining bags in kitchens, agricultural materials and so forth, other additional properties such as the improvement in coloring and weather resistance of woven or non-woven fabrics are demanded. However, when a pigment and an weatherproofing agent are added to woven or non-woven fabric, scum or the like is accumulated on the parts of a fibrillator in a fibrillating step, so that it is undesirable in that unsplit portions and white powder are formed.
Meanwhile, with regard to the reinforced laminate comprising a woven or non-woven fabric and a base material, it is desired to improve its strength and heat resistance.